1. Field of the Invention
The present invention relates to a voltage controller for a vehicle and in particular, to a voltage controller that controls an output voltage of a power generator for vehicles such as a car and a truck.
2. Description of the Related Art
Conventionally, a voltage of a power generator mounted on a vehicle is controlled based on a detected status signal of the generator in which the signal is averaged. For example, in International Publication No. WO2005/031964, a configuration is known in which a power generator state signal is generated by a conduction rate of a switching means (e.g. a duty ratio of a power transistor) connected to a field winding of a power generator for a vehicle. The conduction rate is measured for a predetermined period and an average value being calculated. The generated power generator state signal is transmitted from a regulator to an electronic control unit (i.e., ECU).
In a conventional method disclosed in International Publication No. WO2005/031964, the conduction rate is measured for the predetermined period and averaged. Therefore, the timing content of the power generator state signal is updated is each predetermined period. Even when the state of the power generator for a vehicle changes during the predetermined period, the change is not reflected in the power generator state signal in real-time. As a result, a problem occurs in that reliability of the power generator state signal is low. Because the ECU performs engine control based on an unreliable power generator state signal such as this, engine control becomes unstable. In a worst case scenario, engine control may stop. To prevent a situation such as this, the predetermined period is required to be shortened and the timing at which the content of the power generator state signal is updated is required to be made more frequent. However, in this case, the conduction rates obtained through measurement cannot be sufficiently averaged. Error increases because of the effects of noise and the like. The power generator state signals being outputted remain low in reliability, adversely affecting engine control.